If you’ve stepped outside this summer, you’ve noticed that the bees are back! Bees can be a serious nuisance problem throughout Colorado, particularly in the summer. In overall balance, however, these insects are beneficial in their activities, particularly as predators of pest insects and as pollinators. It is important to distinguish between the various bees because their potential as problems and their control differ. Bees differ from other nuisance insects like wasps in many respects, most fundamentally in their diet. Whereas developing wasps feed on insects and other materials of animal origin bees develop on nectar and pollen.

The honey bee (Apis mellifera) is the only bee, or wasp, that produces a persisting perennial colony. During winter, honeybees survive clustered together within their hive. The queen, the only fertile female, begins to lay eggs in late winter and the young are fed on stored pollen and nectar. At midwinter the size of the colony may only number around 10,000, but numbers increase with the presence of flowering plants that provide food. The majority of bees in the honey bee colony are workers—females that are infertile solely because their diet during development was insufficient for them to mature into a fertile queen. All of the bees — workers, the queen, and the few males (drones) — are dependent on each other and can’t survive for long outside the colony. In this sense, a honey bee colony is often described as being a “super organism” where all the individual insects have essential roles on which the entire colony depends. As a result, reproduction of honey bees is different and requires that the colony periodically subdivide, a process known as swarming. During swarms about half the colony leaves the hive along with the queen and attempts to establish a new colony. The remaining bees then rear a new queen, who may begin to lay eggs three to four weeks after a swarming event.

Most honey bee swarms occur on sunny afternoons in May and June. Immediately after leaving the colony the swarm usually settles nearby clustered on a branch. They then send out bees to scout for suitable nest sites—hollow trees or hives of beekeepers. Once a location is found, the swarm departs to the new home. On the rare occasions when a new nest site is not found, honey bees will begin to produce a wax comb where they originally came to rest. During the summer these types of colonies may expand greatly but invariably are killed out during winter due to exposure. Sometimes honey bee colonies are located within wall voids of buildings. When this occurs the colony must be eliminated as soon as possible. If allowed to develop, large amounts of wax and honey can be produced which ultimately damages the building when the hive dies out or when the combs melt due to extreme heat. Honey bees are not aggressive insects, although they will readily defend the colony. Most stings occur when people step barefooted on bees visiting ground covers or when they accidentally are trapped in clothing. The foraging bees seen visiting flowers do not attack. Unlike other bees and wasps, the stinger of the honey bee is barbed and embeds into the skin. When the bee withdraws the stinger the poison sac is left behind. The bee subsequently dies.

In Colorado, the honey bee is important to the agricultural economy. They are exceptional pollinators and many crops are dependent on them for production including apples, pears, peaches and melons. The value of pollination alone typically exceeds $20 million annually and several million dollars of honey and beeswax products are also produced.

Unlike the honey bee, bumble bees (Bombus spp.) are native to Colorado. Up to two dozen species are present in the state. All are heavy bodied, quite fuzzy and banded orange or yellow and black. Bumble bee colonies are produced annually. Fertilized queens survive the winter and attempt to establish colonies in spring. Oftentimes bumblebee nests occur in abandoned rodent burrows, but they may also occur in other small hollow spaces, particularly if there is insulating debris available. The size of bumble bees varies with the season. Large queens are observed first, followed by the tiny workers she has reared. As the colony increases, the size of the bumble bees that are produced also increases. New queens and males develop by the end of the summer.

A strain of the honeybee, known as the Africanized honey bee, has received considerable attention due to its tendency to readily sting when nests are disturbed. This is a tropical strain of bee that is poorly adapted to areas of cool weather. It does occur in parts of the southwestern United States but is unlikely to ever establish in Colorado.

Solitary bees

The majority of bee species do not produce a colony. These solitary bees include leafcutter bees, digger bees, acute-tongued burrowing bees, and sweat bees. These bees use existing holes, excavate nests in rotten wood and plant stems, or dig burrows in the ground. Within these nests they create a series of cells for rearing young. One group of these, the leafcutter bees line the nest cells with cut fragments of leaves and flower petals. All solitary bees, however, pack the nest cells with nectar and pollen. Although these solitary bees individually produce nests, sometimes many will nest in close proximity. This is particularly common with digger bees.

Solitary bees are not aggressive and stings are quite mild. Most solitary bees can be closely observed and will elicit no defensive behaviors. Perhaps the most common stings that occur are when the sweat bee, which is attracted to moisture, stings when swatted. Males of some solitary bees — which cannot sting — sometimes will make aggressive-looking bluffing flights when defending a territory.

Control of bees

Insecticides used for control of wasps can also be used to kill bees.

Local beekeepers will often collect honey bees that have just swarmed. Collecting swarms typically involves shaking the swarm into a suitable hive box. They will all remain together if the queen is collected. The swarm is then removed at night after the foraging scout bees have returned. Many Colorado State University Extension county offices carry lists of local beekeepers that may be willing to collect honey bee swarms. Honey bees that are already established behind a wall of a building produce special problems. If there is an extensive wax comb and honey, an area of the wall will need to be removed to extract this material. If old combs are left in place after a honey bee colony dies, the wax and honey will melt and flow causing damage. Rodents and insects will also become attracted to this site. It is rare to find beekeepers willing to collect bees that are established behind the walls.

Solitary bees can be difficult to control with insecticides since there are multiple nest entrances and multiple rearing cells within each nest. Often only a portion of the nest is killed and the surviving young emerge the following season. Where large numbers of digger bees nest in close proximity, the permanent control solution is to modify the soil surface. Incorporate soil amendments (e.g., compost, peat moss), establish a plant cover, change the slope or change the watering habits to disturb digger bee nesting sites. The following season, they will move to a new location. Fortunately, these bees are mild tempered. All solitary bees should be conserved whenever possible.

For more information concerning bees, contact the Extension Office at 264-5931.